Jace’s concerns grow about his mental state and turns to Luke for information on his family’s past. Clary and Izzy go after a rogue vampire and Simon hunts for a new apartment.

Someone is out to get Simon and Jace is on the hunt to find out who it is, meanwhile Clary turns to Luke to find a way to help Jace. Alec worries about the future of his relationship after learning more about Magnus’ romantic past.

Clary teams up with Magnus to investigate a recent demon attack. Simon is stunned with he’s visited by someone he never thought he’d see again, and who now won’t seem to leave. Meanwhile, Izzy worries about dinner with her family and a special guest and Luke reaches out to Maryse.

Continuing to track down information on the rumors about misconduct at The Clave’s downworlder prison, Isabelle asks Alec for help. Meanwhile, Magnus succumbs to asking Lorenzo for a favor and Jace takes Clary on a special date.

As the saying goes, “rules are made to be broken.” But what if the rules are there for a reason? Several members of the team must examine the reasoning behind certain rules after consequences to questionable actions come to light. Whether the rules were broken because of love, loyalty or revenge, does the end justify the means?

Jonathan begins his reign of vengeful terror as the Shadowhunters try to find a way to stop him. With only one hope, Clary must make a sacrifice that could have long-lasting implications for all. Meanwhile, wedding bells are in the air for one special couple.